The modern mobile communication increasingly provides omni-directional high quality service to users, and 3rd Generation (3G) technology has occupied the main research field of the current communication field. The 3G Partner Project (3GPP) is devoted to take a Long Term Evolution (LTE) system to be evolution of the 3G system.
FIG. 1 is a structural schematic view of an LTE system supporting Relay Node (RN) according to the related art.
Referring to FIG. 1, in a radio access network of a LTE system, a radio resource management entity comprises a macro base station, such as evolved Node B (eNB) 101, and a Relay Node (RN) 102 which accesses a core network by another macro base station, such as Doner eNB (DeNB) 103, wherein eNBs are connected to one another through an X2 interface, and each of eNBs is respectively connected with a Mobile Management Entity (MME) and a Serving GateWay (S-GW) 104 through a S1 interface; and RN 102 accesses DeNB 103 through a Un interface. The DeNB 103 provides an X2 proxy function between RN 102 and another eNB. The DeNB 103 provides a S1 proxy function between the RN 102 and the MME/S-GB 104. The proxy function of the S1 and X2 includes X2 and S1 signaling specially used in transferring User Equipment (UE) between RN 102 and eNB 101, between RN 102 and MME 104, and between RN 102 and S-GW 104.
The present RN is used to support an immobility position rather than supporting mobility between different cells. A problem confronted by operators is that in a high-speed railway, such as a train that runs at a 250-350 km/h, the service quality of the present RN is not satisfied with the requirements of the operators, such as high noise, great penetration loss, serious Doppler Frequency shift, and low handover success rate and the like. For these purposes, the operators provide a research project about a mobile RN. The mobile RN directs to address the problems existing in the RN to improve service quality in the high-speed railway for a good satisfaction with the users' requirements.
A process of a Tracing Area Update (TAU) in the LTE system is described below with reference to FIG. 2.
FIG. 2 is a TAU flow diagram according to the related art.
Referring to FIG. 2, the TAU flow comprises the following operations.
In operation 201, a UE sends a TAU request message to an eNB. Specially, a UE sends a TAU request to an eNB through a Radio Resource Control (RRC).
In operation 202, the eNB sends a TAU request message to MME through S1.
In operation 203, a new MME obtains an address of an existing MME according to a Global UE Temporary Identifier (GUTI) received by the UE. A new MME sends a context request to the existing MME so as to request the context information about the UE.
In operation 204, the existing MME sends a context response message to the new MME.
In operation 205, executing a process of authentication and certification to the UE. Such process is selectable and executed under certain circumstances.
In operation 206, the new MME sends a context confirmation message to the existing MME.
In operation 207, the MME sends a modification bearer request message to the S-GW/Packet Data Network Gateway (PDN GW). Herein, a detailed description of the operations between the S-GW and the PDN GW is omitted.
In operation 208, S-GW/PDN GW sends the modification bearer response message to the MME.
In operation 209, the MME sends an update location request to a Home Subscriber Server (HSS).
In operation 210, the HSS sends a cancel location to the existing MME.
In operation 211, the existing MME sends a cancel location confirmation message to the existing HSS.
In operation 212, the HSS sends an update location confirmation message to the MME.
In operation 213, the MME sends a TAU accepting message to the UE.
In operation 214, if the GUTI is changed, the UE sends a TAU accomplishment message to the MME to confirm acceptance of the new GUTI.
As illustrated in the TAU process mentioned above, several messages are used for each UE to execute a TAU process every time. When the train runs at a high speed, both RN and UE are moving, if a plurality of UEs execute the TAU process at the same time, it will bring about an unnecessary waste of network resources and jam the network.
Therefore, there is a need to provide an effective technical solution in order to address the problem that the UE frequently executes a TAU process.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.